Which of the following sets of ordered pairs does not represent a function?
A] {(0, 1), (1, 2), (3, 4), (2, 2)
B] {(-2,2),(1,2),(5,4),(6,2)}
C] {(0,1),(0,2),(-3,6),(2,7)}
D] {(-1,3),(6,5),(3,1),(2,1)}